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Abstract

Infectivity and inflammatory responses during persistent and reactivated Q fever in mice

Victoria K. Baxter, Masako Andoh, Kasi E. Russell-Lodrigue, and James E. Samuel

Department of Microbial and Molecular Pathogenesis, Texas A&M University System Health Science Center, Victoria BaxterCollege Station, TX 77843-1114, USA

 

STRUCTURED ABSTRACT

Objective – To monitor changes in cytokine response to Coxiella burnetii infection during long-term colonization in mice.

Animals or Sample Population – 56 female C57BL/6J mice

Procedure - C57BL/6J mice were infected intraperitoneally (IP) with one of three isolates of C. burnetii: PG-I isolate Nine Mile RSA493, PG-IV isolate KQ154, or PG-V isolate GQ212. As a control, one group of mice was given phosphate-buffered saline IP rather than C. burnetii challenge. Body weights of the mice were recorded weekly and weight changes analyzed using body weight index. Peripheral blood samples were taken at 0, 7, 14, 21, 28, 35 days post infection, and cytokine levels at each time point were analyzed by a cytokine assay.

Results – Mice infected with C. burnetii showed temporal weight loss at 7 DPI followed by temporal weight gain at 14 DPI that was not PG-specific before returning to baseline weight. IFN-g, TNF-a, and RANTES levels all increased in all mice infected with a C. burnetii isolate. Cytokine levels in PG-IV infected mice had the least pronounced change over time and returned to baseline levels in all cases. PG-I and PG-V infected mice displayed a more pronounced and persistent cytokine response that continued to remain elevated for TNF-a (PG-I) and RANTES (PG-I and PG-V).

Conclusions and Clinical Relevance – Cytokine response to C. burnetii infection is PG-specific, and dose level of C. burnetii plays a direct role in the level of response. This aids in the understanding of C. burnetii infection pathogenicity and the host defense system against infection.